Dementia and cognitive impairment associated with stroke are an important but enigmatic public health problem. As many stroke patients are elderly, concomitant pathophysiologic mechanisms may play a role in the genesis of their dementia. Now, novel quantitative MRI imaging technology is available as a potentially powerful in vivo research tool that may identify factors that contribute to dementia and cognitive impairment in patients with stroke. The major aim of this proposal is to identify risk markers such as hippocampal and entorhinal cortex volume, white matter dysfunction, stroke volume, and generalized brain volume by quantitative MRI technology that may contribute to dementia and cognitive impairment in stroke patients. The applicants propose to use a new technology of quantitative MRI analysis, diffusion tensor scanning, to study diseased white matter of the brain. The proposed analysis will take into account MRI and other factors that may be important in the genesis of dementia after stroke by case-control methodology among ischemic stroke patients who do or do not develop dementia. The applicants propose to study the contribution of MRI markers of Alzheimer's disease (AD) in stroke patients. In those stroke patients who do not show quantitative MRI markers for AD, it may be possible to begin to define 'vascular dementia.' The findings will be validated by neuropathologic correlation among patients who come to autopsy. By defining the role of quantitative MRI analysis in dementia patients after stroke, the applicants propose to clarify the concept of 'vascular dementia.' They state that refinement in our knowledge of mechanisms and causes for dementia in stroke patients may lead to an improvement in prevention and treatment strategies.